Should you add a detached ADU or an attached ADU to your backyard? Don’t make a hasty decision because building an ADU is important and there are benefits and cautions for each style.
What Is An ADU
Let’s start with an ADU definition. It is an acronym that stands for Accessory Dwelling Unit- a secondary home that shares land with the main home.
An ADU is different from a guest house because it a fully independent living space with a complete bathroom and kitchen.
Detached ADU plans do not include any shared walls or structural elements with the main structure. In most jurisdictions, there is at least 6 feet separation between the main house and the ADU or backyard house.
Detached accessory dwelling unit plan can include detached garage adu designs, custom site built adu design, and prefab adu structures.
An attached ADU shares at least one wall with the main dwelling. It could be carved from existing space in the house, such as a family room or former primary bedroom suite, or converted basement or attic space.
New construction added to the side or on top of the existing home is another way to add an ADU. It must have its own exterior entrance in order to qualify as an ADU.
How Big Can A Detached ADU Be?
Attached ADUs are considered JADU or Jr. ADUs and are limited to 500 sf in most jurisdictions.
A detached ADU is often referred to as a backyard house can be as large as 1200 sf, depending on local rules. Almost every jurisdiction will allow an 800 sf ADU.
READ: California ADU Laws 2022
Which ADU Costs More To Build?
As a general rule attached ADUs are going to be less expensive than a detached, stand-alone ADU construction.
How much does it cost to build a detached ADU? This is a very hard question to answer without knowing the details of your particular site and the specific design of your detached ADU. Online prices will range from $30,000 to $300,000 for seemingly similar units and sizes.
A garage ADU design is also a detached ADU and it can be a very cost-effective way to add an ADU.
Beware of “Cheap”
The low cost is attractive, but you might regret that decision in just a few years. Good quality ADU construction is long-lasting and thoughtful ADU floor plans deliver maximum flexibility as your lifestyle changes.
Converted, existing space in the main house could cost as little as $25,000, but a new addition can run into the hundred thousands, especially if it is a second-story addition.
READ: Cost of Prefab ADU
Can I Get Utilities To A Detached ADU?
The electric and water utilities for your detached ADU are usually tied into the main house.
This is true even if there is a solar energy panel system (SEE: ADU DIGGS Features).
Most homeowners will need to increase the size of their existing electric panel to accommodate the needs of the ADU.
An attached ADU is usually less resource-intense and an upgraded electric service is less likely.
You can install separate utility services for your detached ADU, but it will add significant costs.
Which ADU Style Rents For The Most Money?
A detached ADU will give the best ROI for rental income. Great site design will orient the ADU for maximum privacy and outdoor areas for each unit.
It is even possible to create this privacy on a small lot.
An attached ADU offers the lowest rental income as the units have less privacy and generally fewer amenities.
READ: Cash flow for ADU
ADU Lifestyle Choices
The way you plan to use your ADU can also influence your decision to add an attached ADU or a detached ADU.
A detached ADU will occupy a huge portion of your backyard unless you have an unusually large piece of land. Will you get more value from the ADU or from the open space in your yard?
It is possible to use ADU design to create a multi-purpose structure that allows most, if not all of your backyard activities.
Which ADU Increases My Property Value
The maximum contribution to your property value is a new detached ADU, followed by an ADU garage conversion. Currently, a new detached ADU can increase your resale value by $300,000 or more, depending on your neighborhood resale values.
A garage converted to an ADU offers significantly less value add. Values can even decrease in areas where garages are highly valued.
An attached ADU is the least valuable and can also detract from your home’s value if it is poorly designed or executed.
We Can Help You Choose The Right ADU
With over years of experience in residential real estate, we can help you assess factors like potential impacts on property value and rents.